Initially, I looked for pump specific replacement parts online, but, could not find them. Napa was the logical next step.

In the cylinder head I have two flat seals on the top and bottom of the cylinder. It is not like the O-ring for the shaft. I am not sure if we are talking about the same part.

The easiest way to fix this is to stop by my house and get what you need. I have plenty of extra pump parts, so you are welcome to take what ever you can re-use. I was going to throw some of it away soon due to limited space. I am in North Seattle.